This invention relates to solids-emulating compositions, and concerns in particular solid-particulates-containing paintable or mouldable materials for functional and/or decorative purposes.
There are many occasions when it is desirable, for either functional or purely aesthetic reasons, to give some article or one solid material a coating or appearance of another solid material. For aesthetic purposes, for instance, it might be thought attractive to provide a non-metal objectxe2x80x94a wooden carving or a plaster mouldingxe2x80x94with the visual appearance of real metal, such as copper, iron, brass or bronze. Similarly, it might be desirable to provide a non-mineral object with the appearance of rock or stone. For functional purposes, for example, it might be desirable to form on a substrate a layer with a high electrical impedance and with the appearance of metal. And from a practical point of view it is clearly desirable that such coatings be applicable in as easy a manner as possiblexe2x80x94by being painted on with a brush, sayxe2x80x94and that after application the finished surface lend itself to the kind of physical or chemical treatment that a real metal or mineral surface would allow, such as burnishing or polishing, or some sort of chemical alteration. The invention proposes one way of achieving this capability, by using a curable resin-based composition carrying dispersed therein some suitable particulate solid.
It is already known to provide settable curable resin-based metal compositions, primarily for decorative purposes such as making solid objects like busts using a mould, but those presently available tend to be rather inflexible in their mode of use (with a fairly limited number of applications), as well as being quite difficult to employ (the chemicals involved are inclined to be hazardous to health). One such composition, generally intended for making solid objects such as figurines, busts and the like, is provided in three constituent partsxe2x80x94the resin, the metal, and a catalystxe2x80x94which the User must mix together immediately prior to use (and there is then only a limited amount of time to employ the resin before it sets). Moreover, not only is this type of resin-based substance difficult and unpleasant to use, but in general it cannot easily be applied to a surface with a brush, nor does the finished surface readily lend itself to subsequent physical or chemical treatment.
Another such composition, or group of compositions, is described in the 1978 Specification of published French Patent Application No: 2,364,256 (the corresponding German Offenlegungsschrift is No: 27 05 683). These compositions, like some of those of the present invention, are intended to be employed to provide metal (or metal-like) coatings of one sort of material on substrates of another, to give the substrate a different appearance or properties, but they, too, are provided in separate constituent parts which are mixed just before use. The compositions, too, are in reality difficult and unpleasant to use, and though they can be applied to a surface with a brush or like implement it is not easy to achieve a good finish this way (and nor do the coatings adhere well to the underlying material surface). Moreover, the formed coatings have right from the start a surface xe2x80x9cskinxe2x80x9d or xe2x80x9cfilmxe2x80x9d of opaque resinous material that effectively totally obscures the included metal, and this skin has to be removed after the resin has setxe2x80x94a process which, according to the Specification, requires considerable amounts of abrasion (using coarse abrasives, such as steel wool, abrasive brushes and abrasive powder) to remove the film-forming resin, followed by several more separate xe2x80x9cpolishingxe2x80x9d stages (using finer abrasives or polishing disks or fabrics). This produces residual dust, which is unhealthy and environmentally unfriendly. And if the substrate surface is rough, or even merely dimpled, it is difficult, if not impossible, to remove from the surface sufficient of the skin to reveal the included metal in the depressed areas without actually taking almost all of the layer off the protruding areas.
The invention in one form suggests a novel solid-particulates-containing composition that deals with these problemsxe2x80x94a composition that can be available ready made (rather than having to be made up immediately prior to use) but with a substantial shelf life; that can truly be applied like a conventional paint, using a simple paint brush or roller; and that gives with almost no further treatment other than a dust-free light polishing or burnishing an excellent finish which lends itself to a variety of uses and treatments as if it were the surface of an ordinary object of that solid. More specifically, the invention proposes a solid-particulates-containing composition comprising from 5% to 80% by volume of the chosen particulate solid dispersed within either a vinyl acetate polymer composition or an acrylic polymer compositionxe2x80x94especially such a composition which contains, per 100 volume parts of the chosen polymer, some water, and particularly from 25 to 80 parts of water. To date, the best compositions seem to be those aqueous compositions that contain both vinyl acetate polymer and acrylic polymer, the amounts being such that, per 100 volume parts of vinyl acetate polymer, there are from 5 to 80 parts of acrylic polymer and from 30 to 80 parts of water. The great advantages of such a composition over those of the Art stem mainly from its aqueous naturexe2x80x94not only does this mean that the compositions, curing (as they do) by loss of water following application, remain usable in the pot for weeks, if not months, after being opened, but it also means that the compositions can be thinned (within limits) to adjust their consistency, applicability and spreading power simply by adding (tap) water, and that they are essentially non-toxic (the normal water-dispersible vinyl acetate polymer and acrylic resins are effectively harmless, and there are no unpleasant organic solvents/diluents or catalysts/hardeners). In addition, by selecting these particular resinous materialsxe2x80x94a water-dispersible vinyl acetate polymer and a water-dispersible acrylic resinxe2x80x94there is provided a coating which, on drying, appears to have no, or substantially no, resin material in the form of a skin on top of, and obscuring, the particulate solid, so that with even the most minimal polishing or burnishing (and without the use of any real abrasives) the coating takes on the appearance, and even some of the properties, of the particulate solid.
In one aspect, therefore, the invention provides a composition usable for application as a coating to a surface, the composition being an aqueous dispersion of solid particles within a resinous carrier and comprising:
from 5% to 80% by volume of particulate solid dispersed within
either a vinyl acetate polymer composition or an acrylic polymer composition.
There are preferably from 25 to 80 volume parts of water per 100 volume parts polymer.
Though the composition of the invention is one which contains either vinyl acetate polymer or acrylic polymer, these are not exclusive, and indeed the most preferred compositions of the invention contain both (as noted above). Very preferably, therefore, the invention provides a composition for applying as a coating to a surface, the composition being an aqueous dispersion of solid particles within a resinous carrier and comprising:
from 5% to 80% by volume of particulate solid dispersed within
a vinyl acetate polymer composition containing, per 100 volume parts of vinyl acetate polymer,
from 5 to 80 parts of acrylic polymer, and
from 30 to 80 parts of water.
The invention in one form provides a composition for applying a coating to a surface. The coating is a coating of real solidxe2x80x94whichever solid, or combination of solids, has been employed as the particulate solidsxe2x80x94and, depending on the physical form of the particles, and the amount thereof, may actually form an effectively continuous solid layer extending over the surface carrying the coating. Depending on the nature of the solidxe2x80x94if it were copper, nickel, silver or gold, for examplexe2x80x94such a layer could be electrically conductive, and so might be of value in the formation of articles such as printed circuit boards, and heating elements, or as a base for a subsequent electroplating operation.
The composition of the invention in one form is for applying a coating to a surface (although it may doubtless be utilised for other purposes, such as, for example, being xe2x80x9csetxe2x80x9d in a mould or shaped by hand to form a solid article; this is discussed further hereinafter). This surface can take almost any physical form, and can be of a wide variety of substrates, including metal, wood, polystyrene (and other plastics of many sorts), plaster, glass, paper, acetate, cardboard, hardboard, concrete, brick, and ceramics. Any substrate that does not give a good tooth to the composition can first be coated with a primer. Polystyrene, which is normally difficult to adhere to without softening of the polystyrene, can readily be adhered to by compositions of the invention.
The preferred compositions of the invention comprise a dispersion of solid particles in an aqueous resinous carrier dispersion. The solid can be any of a vast range, including: metals, such as copper, brass, nickel brass, bronze, silver, aluminium and gold, and even relatively hard metals like iron, steel, nickel and titanium; minerals, such as granite, marble, mica, sandstone, slate, and fired or unfired clay (such as terracotta); other solids, such as carbon and glass; and mixtures of two or more of these. The particles can be of any suitable size small enough to stay dispersed without the need for frequent or too-violent agitation (although on the shelf compositions of the invention may in time show signs of some settling-out, they can be re-dispersed by simple stirring and/or shaking), and the commercially-available powdered solids seem quite satisfactory.
The amount of solid employed in the compositions of the invention can vary over a wide range, though obviously very small amountsxe2x80x94less than 15%, sayxe2x80x94may require a number of coats to be applied to the desired surface to achieve a satisfactory result, while very large quantitiesxe2x80x9450% or more, sayxe2x80x94may result in a final composition that is too heavy in solid to be readily workable as a paint. For a paintable composition the range should be up to 50% by volume of particulate solid, preferably 5% to 45%, with an especially preferred range being from 35% to 45%. The most convenient compositions are those that include amounts at the upper end of this range. However, for a solid-object-forming composition, to be described hereinafter, the corresponding figures are somewhat higher, typically 70% and from 50% to 65%.
The compositions of the invention comprise solid particles within either or both (a mixture) of an acrylic polymer and a vinyl acetate polymer. This latter polymer may be a plain homopolymerxe2x80x94a polyvinyl acetatexe2x80x94or a heteropolymerxe2x80x94an ethylene vinyl acetate, for instance. In the preferred compositions the purpose of the vinyl acetate polymer is to act as the main carrier for the solid particles, and to provide a firm but flexible layer that adheres well to the surface of the underlying substrate. So far as can be determined the vinyl acetate can be any one or more of the varieties of vinyl-acetate-containing products used or suggested for use as a sealant, binder or adhesive, and many such products are commercially available. A typical plasticised vinyl acetate homopolymer has a glass transition temperature (Tg) of around 10xc2x0 C. (the majority of vinyl acetate polymers have Tgs of from 5xc2x0 C. to 30xc2x0 C.).
The compositions of the invention utilise one or both (a mixture) of vinyl acetate polymer and acrylic polymer. In the mixture the primary purpose of the acrylic polymer is to soften the vinyl acetate polymer, and leave it workable for sufficient time to allow the coating to be formed and spread out by brushing. The amount of acrylic should thus be sufficient for this purposexe2x80x94per 100 volume parts of vinyl acetate polymer, 5 parts of acrylic polymer are usually just enough to get the vinyl acetate polymer into a workable form, while with more than 100 volume parts the composition will generally be too soft and runny to be very useful. A more convenient upper limit is 80 volume parts, while the more preferred compositions contain amounts at the lower end of the rangexe2x80x94thus, from 15 to 35 volume parts, and especially 25 volume parts.
The acrylic polymer can be any one or more of the many known polymers of this sortxe2x80x94usually available as aqueous emulsions of the polymer per sexe2x80x94and typical such products are based on acrylic or methacrylic acid derivatives and have Tg values of around 35xc2x0 C. (the majority of water-dispersible acrylic resins have Tgs of 35xc2x0 C. to 70xc2x0 C.).
The preferred compositions of the invention comprise particulate solid(s) dispersed within an aqueous polymer compositionxe2x80x94that is, a composition of the polymer materials themselves dispersed in water. The water is primarily merely a thinner and extender, mainly to dilute the polymerxe2x80x94the vinyl acetate polymer, sayxe2x80x94and so render it more workable, and should be used in an amount sufficient for this and to result in a pasty, brushable composition with a reasonable shelf life. Small amounts of waterxe2x80x94less than 30 parts, sayxe2x80x94cause the composition to set too quickly, and to build up on the brush, so being difficult to apply, while large amountsxe2x80x94more than 80 parts, perhapsxe2x80x94make the composition too runny, and cause it to take too long to set (and to need too many coats to build up a layer of the required thickness), 40-70 parts seems a reasonable quantity. Incidentally, it is possible to xe2x80x9cthinxe2x80x9d the compositions of the invention not just with water but also with one of the proprietary acrylic thinners, such as Airbrush Medium.
A particularly-preferred polymer mixture composition of the invention is one that contains, per 100 parts of vinyl acetate polymer, 25 parts of acrylic polymer and 50-70 parts of water, and, for each 30 parts of this preliminary composition, 20 parts of solid powder.
The compositions of the invention may settle out, and therefore it may be beneficial to include one or more of a particle-suspending surface active agent and a thickening agent. Perhaps surprisingly, many common surfactants will suffice, even conventional washing-up liquid, while a useful thickening agent is AQUA PASTO (an acrylic thickener available from Windsor and Newton). A particularly-preferred detergent-incorporating polymer mixture composition of the invention is one that contains, per 100 parts of vinyl acetate polymer, 25 parts of acrylic polymer, 50 parts of water, 1.5 parts of unscented, colourless liquid detergent, and, for each 30 parts of this preliminary composition, 20 parts of solid powder. And an especially preferred variant of this latter composition is one that additionally contains, per 100 parts of vinyl acetate polymer, 1 part of a thickener such as AQUA PASTO.
The compositions of the invention are primarily for applying a coating to a surface. However, theyxe2x80x94or modified versions of themxe2x80x94may be utilised for other purposes, such as, for example, forming very thick layers or coatings on a substrate, or even being xe2x80x9csetxe2x80x9d in a mould to form a solid article. More particularly, it has been found that the compositions can be xe2x80x9cbulked outxe2x80x9d, using a fibrous material such as cellulose (paper) conveniently added as an aqueous pulp (and so providing some or all of the water required in the composition). In this way the compositions become putty-like, and can be handled and moulded into three-dimensional shapes that in time set to become stable solids. Such solids can be cut or carved into other shapes, and when given an appropriate xe2x80x9cfinishingxe2x80x9dxe2x80x94such as by brushing, polishing or burnishingxe2x80x94are indistinguishable from the xe2x80x9crealxe2x80x9d thing (that is, an object made of metal, stone, or whatever the particulate solid was).
The compositions of the invention can be made by simple admixture of the ingredients, though it is convenient first to make a preliminary composition by mixing the water and polymers, and then to add to this the solid particles and any other components. Proper mixing (and subsequent film-formation) of the non-solids parts of the compositions may be improved by the addition of small amounts of co-solvents (typically water-miscible glycols), while thorough dispersion (and subsequent re-dispersion) of the solids can be aided by including small amounts of a detergent, a flow-control agent such as molybdenum or graphite, or a suitable thixotropic material. Re-dispersion by shaking can also be assisted by including a small mixerxe2x80x94a ball bearing or twoxe2x80x94in the container. Excessive foaming can be dealt with by incorporating a suitable anti-foaming agent. Film-formation subsequent to application may be improved by incorporating a suitable coalescing solvent.
Naturally, the invention""s compositions can contain such bioactive materials as fungicides, bactericides and bacteriostats.
In the main, the invention""s compositions can bexe2x80x94and are primarily intended to bexe2x80x94applied with a brush or roller, as if they were paint (though they can be sprayed with the appropriate equipment). It is therefore especially simple to use two different metal or other solid compositions in conjunction to create effects as requiredxe2x80x94for instance, picking out certain objects on, or parts of, a surface with one metal, and so having one appearance, while the restxe2x80x94the background, perhapsxe2x80x94is of a different metal. Thus, a sculptured or moulded surface with the appearance of a bas-relief might have the raised parts in copper and the recessed parts in iron.
One of the advantages of the invention""s compositions is that the surface resulting from use of such a composition can thereafter be modified almost as if it were a real solid object. While the coating is still relatively fluid (and has not set completely) it can be given a stippled surface by dabbing it with a sponge, whereas once it is dry it can be gently rubbed with, for example, a soft, fine suede brush (this tends to produce no xe2x80x9cdustxe2x80x9d residue) to brighten the finish (note that this rubbing xe2x80x9cpolishesxe2x80x9d the surface rather than abrading it away). Furthermore, for metal, well-known metal cleaners (such as DURAGLIT or BRASSO) can maintain a previously-attained shine on the metal, or the metal can be treated with one or more of a number of known chemical substances that are used to produce specific effects on metals (for instance, COPRA can be used to verdigris a painted-on copper layer of the invention just as it can a real copper object). Moreover, the finished surface can be coated in a manner known per se to protect the surface against such things as tarnishing and corrosion.
Though the compositions of the invention may find their primary use being for aesthetic reasons, and so perhaps as a decorative paint, they also have a number of functional, possibly industrial, uses. With sufficient metal included the paint might conduct electricity, and might therefore be usable in semi-conductor and circuit technology. Other compositions might be employed to create coatings usable in interference shielding technology (for example, a carbon-containing composition could be usable to shield against radio-frequency signal interference, whilst a nickel-containing composition could be usable to shield such things as computers against static electricity), while an iron-containing composition has magnetic properties. The use of the composition as a preliminary layer in a plating process might also be feasible. With a titanium-containing composition, it is very easy to obtain a titanium finish on a surface, even though titanium itself is extremely difficult to work, and especially to weld and to deform.
Although the invention has its primary application in providing metallic coatings, it is also applicable to the provision of mineral-like and other coatings.
Moreover, the invention is applicable to providing mixed solids coatings; for example, a composition containing a mixture of sands and rustable metal powder can give a real sandstone effect after rusting of the metal powder.
The invention in its primary aspect is a composition that can be used to give to a substrate of one material the appearance of another material, and in another aspect the invention provides just thatxe2x80x94a method for supplying the surface of a substrate of one material with the appearance of another material, in which method there is applied to the substrate surface a composition of the invention.
As explained hereinbefore, the formed surface coating may be acceptable and sufficient in itself; however, if required, or appropriate, the formed surface coating may thereafter be given a further treatment to modify or enhance it. For example, while still slightly xe2x80x9cwetxe2x80x9d, it can be dabbed to give it a stippled finish, while when fully dry it can be polished, burnished, buffed and so on to give it a shine. One particular advantage of many of the metal coatings or solid objects formed by the compositions of the invention is that they are xe2x80x9cmutuallyxe2x80x9d burnishingxe2x80x94that is, one coated substrate or solid object can be rubbed against another, and both are burnished. For example, a solid object made from a composition of the invention can be used as a burnishing tool on a coated substrate.
The compositions of the inventionxe2x80x94perhaps it should be said the preferred compositions of the inventionxe2x80x94are each an aqueous dispersion of solid particles within a diluted mixture of a resinous carrier and comprising from 5% to 80% by volume of particulate solid dispersed within a vinyl acetate polymer composition containing, per 100 volume parts of vinyl acetate polymer, from 5 to 80 parts of acrylic polymer, and from 50 to 80 parts of water. As noted hereinbefore the preferred materials for use as the vinyl acetate polymer and the acrylic polymer have glass transition temperaturesxe2x80x94Tgsxe2x80x94of up to 10xc2x0 C. (perhaps up to 20xc2x0 C.) and from 30xc2x0 C. to 70xc2x0 C. respectively. It now seems possible that this particular propertyxe2x80x94the Tgxe2x80x94of the polymer materials is important in explaining the desirable effects achieved with the compositions of the invention, and indeed that it is each material""s Tg, rather than its chemical nature (polymeric vinyl acetate or acrylic) that determines whether the resulting composition is suitable for making layers/coatings of the sort here desired. Accordingly, in yet another aspect this invention provides a composition for applying as a coating to a surface, the composition comprising an aqueous dispersion of solid particles within a diluted mixture of a resinous carrier and comprising:
a particulate solid;
a particulate organic film-forming polymer (or copolymer) having a Tg of below 10xc2x0 C.; and
a particulate organic film-forming polymer (or copolymer) having a Tg of above 30xc2x0 C.
Naturally, the invention also provides a method for supplying the surface of a substrate of one material with the appearance of another material, in which method there is applied to the substrate surface a composition as just definedxe2x80x94and thereafter performing any subsequent treatment stage, such as polishing or burnishing, as may be required.
According to a further aspect of the present invention there is provided a composition for working in the manner of a paint or putty, comprising an aqueous dispersion of solid particles within a mixture of a carrier substance and a carrier-softening substance, the carrier substance serving to provide a firm anchorage for the particles.
The following Examples (in which all parts are by volume) are now given, though by way of illustration only, to show details of particular embodiments of the invention.